As a display of, for example, televisions, personal computers, smartphones, tablet computers, display devices comprising an organic EL element formed from organic material have been developed. The organic EL element emits light by applying voltage to the organic material disposed between an anode and a cathode. Light emitted from the organic material spreads in an isotropic fashion and is extracted from the device to the outside.
In the display device equipped with such an organic EL element, it is important to efficiently extract light emitted from the organic material to the outside of the device in order to suppress power consumption. Particularly, in mobile devices such as smartphones and tablet computers, it is necessary to control power consumption to retain the battery for a long time. Therefore, the improvement in the efficiency of light extraction is desired.
In recent years, for the improvement of the light extraction efficiency, an organic EL element comprising a reflection structure (reflector) has been developed, by which light emitted from an organic material is reflected by a metal electrode or an insulating film to be output to the outside of the device.